Governor suddenly stopped working on MB200

[Detasman]

The governor on my son's MB200 (Warrior 200) suddenly stopped working. The governor arm no longer returns to its resting position on its own. This causes the throttle at the carburetor to sit at about half open without applying any hand throttle action. A bad situation, as the bike races wildly without applying the hand throttle. I can move the governor arm into its resting position by hand which returns the throttle back to its normal idle position. I have temporarily remedied this by adding a spring to the governor arm to pull it back. The spring tension can be overcome by applying hand throttle. The throttle at the carburetor then gradually opens and operates as normally, except for the fact that there is no longer any governing action at any rpm.

All the other springs in the throttle path seem to be connected. One heavier spring and one thin spring.

I have adjusted the throttle stop to prevent the bike from overrevving when the hand throttle is fully opened.

Any clues as to what went wrong and how I can permanently fix?

 

[Fat Tony157]

It could be a couple things. The throttle linkage could have loosened up where it connects to the internal governor arm under the gas tank. Or the internal governor could have actually failed entirely. I would start by popping off the gas tank and checking if the linkage is connected properly. Next step past that would probably be to pull the side crankcase cover and inspect the internal governor components.

 

[Detasman]

It could be a couple things. The throttle linkage could have loosened up where it connects to the internal governor arm under the gas tank. Or the internal governor could have actually failed entirely. I would start by popping off the gas tank and checking if the linkage is connected properly. Next step past that would probably be to pull the side crankcase cover and inspect the internal governor components.

If it is an internal failure (which I fear it is), do I run the risk of loose parts inside the engine causing further damage?

 

[Fat Tony157]

Yes, usually those governor pieces will scatter in the bottom end. I wouldn't risk running the engine anymore until you clean that out.

 

[Detasman]

Yes, usually those governor pieces will scatter in the bottom end. I wouldn't risk running the engine anymore until you clean that out.

So, my small engine game is pretty poor. I stand a good chance of getting the tank off but I'd have no idea what to be looking for externally to tell if the governor arm is properly connected to the engine. I would need to draw the line at opening up the crankcase. I think it might be time to call in the A-Team.

Any Southern Maryland minibike experts out there?

 

[Fat Tony157]

I had a similar engine sitting around with the gas tank off of it so I grabbed a pic. This should give you an idea of about where it should be. The pin has a flat side thats usually lined up with the slot on the governor arm.

 

[EVOL Tweety Bird]

Tis nothing to removing the side cover, pop off the chain and clutch, drain the oil, and unbolt the side cover.
Most of these engines have a plastic governor gear, which can break. Honestly to get a better feel for the job there are bunch of YouTube videos that show how the governor is removed. Not saying to remove one on a stock engine, but the videos will show you the steps needed to get to the governor for inspection.

The governor normally holds the throttle open for starting, soon as the engine starts, the weights on the governor open up to pull the throttle back to the closed/idle position.